[Issue 11503] New: Type system breaking caused by implicit conversion for the value returned from pure function
d-bugmail at puremagic.com
d-bugmail at puremagic.com
Mon Nov 11 20:13:30 PST 2013
https://d.puremagic.com/issues/show_bug.cgi?id=11503
Summary: Type system breaking caused by implicit conversion for
the value returned from pure function
Product: D
Version: D2
Platform: All
OS/Version: All
Status: NEW
Severity: critical
Priority: P2
Component: DMD
AssignedTo: nobody at puremagic.com
ReportedBy: k.hara.pg at gmail.com
--- Comment #0 from Kenji Hara <k.hara.pg at gmail.com> 2013-11-11 20:13:27 PST ---
From: http://forum.dlang.org/post/l5o3tq$jof$1@digitalmars.com
If an immutable value is returned by pure function, compiler _must_ not
implicitly convert it to mutable.
Test case:
import std.stdio;
struct S
{
immutable(S)* s;
this(int) immutable pure
{
s = &this;
}
int data;
}
immutable(S)* makes() pure
{
return new immutable S(0);
}
void main()
{
S* s = makes(); // s is mutable and contains an immutable reference to
itself
pragma(msg, typeof(s)); // mutable
pragma(msg, typeof(s.s)); // immutable
writefln("%s", s); // same address
writefln("%s", s.s); // same address
//s.s.data = 7; // this is immutable
s.data = 3; // but this is not!!!
}
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